Comparative evaluation of radiographic and computed tomographic findings in dogs with bilateral medial coronoid disease (MCD) presenting with unilateral forelimb lameness

Objectives The purpose of this study was to compare the radiographic and computed tomographic (CT) findings of dogs with diagnosed bilateral medial coronoid disease, which showed clinically only unilateral lameness of the forelimbs. Materials and methods Medical records, including radiographs and CT images of dogs with diagnosed bilateral MCD showing only a unilateral forelimb lameness clinically were reviewed retrospectively. Depending on the gait of each dog we established two groups to investigate their radiographs and CT data comparatively. Group I: affected non-lame limb. Group II: affected lame limb. Several evaluation systems were used to assess which factors are important for clinical decision making and a patient tailored therapeutic plan. Results Data from 84 affected elbow joints (42 dogs) diagnosed with MCD by computed tomography were included. Both the radiological and the CT analysis showed that there are significant differences between Groups I and II. Group I had a lower modified International Elbow Working Group Score (IEWG), the values of the Trochlear notch sclerosis were only slightly deviated, and this group showed less often a dislocation of the fragment compared to group II. Furthermore, the size of the fragment (both the median and the mean value) of the forelimbs from group II was almost twice as big as the one from group I. The following sizes of the fragments were calculated (group I versus (vs.) group II)—median: 0.09 cm2 vs. 0.16 cm2, mean value: 0.112 cm2 vs. 0.202 cm2. It could be shown that a larger fragment is more likely to dislocate than a smaller one. Clinical significance This study provides some evidence towards a better understanding of which diagnostic parameters and findings might be important in clinical decision making. Nevertheless, a “decision tree” for the correct therapy of MCD could not be determined in this study.


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A total of 42 dogs are considered. The analysis is performed using two data sets. One data set contains general information regarding the dog and the disease. The dataset contains 82 observations, since each dog has two observations (one for each elbow). The other data set contains information about the radiographs. For a difference between therapies, the IEWG (International Elbow Working Group) score and the TNS (Trochelar Notch Sclerosis value) score are used. The dataset contains 82 observations. In the following, score variables are understood as the IEWG (International Elbow Working Group) score and the TNS (Trochelar Notch Sclerosis value) score. Similarly, radiographs are considered in relation to the age class of the dog. Furthermore, variables describing the disease of the elbow joint are considered descriptively and also grouped by therapy and age class are considered descriptively. Variables related to the disease of the elbow joint are also referred to as CT variables in the further course.

Description
The description separates into several subsections. In the first section an unstratified description is given, in the second section an unconnected stratified description is performed.

Unstratified descriptor
The following is a descriptive summary of general information about the treated dogs. In Table 3.1, metric covariates are reported using the mean (Mean), standard deviation (SD), and number of missing values. Categorical covariates are described using absolute (N) and relative frequencies (%).

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3 Table 3.1: Description of the general data concerning the dogs In Table 3.2, the data regarding the variables related to the disease of the dog and regarding the variables related to the radiographs are given.  Table 3.3 the variables taken from the X-ray images can be seen. Table 3.3: Description of the values from the X-ray images

Context analysis
In the first subchapter, the variables from the radiographs are considered grouped according to the age class and the degree of lameness of the limb. In the second chapter, the CT variables are grouped according to the age class and the degree of lameness of the limb.

Observation of the variables from the X-ray images
The following tables reflect the statistical ratios of the TNS value grouped by age class (Table 4.1) and by the degree of lameness of the limb (4.2). The corresponding boxplots can be seen in Figure 4.1 and 4.2.

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The following tables show contingency tables in which the IEWG value is plotted together with the grouping variables age class (Table 4.3) and degree of lameness limb (Table 4.4). The plot with the grouping variable lameness degree limb is a linked sample. The percentages refer to the entire sample and not to row totals. International Elbow Working Group

Conclusion
The 42 dogs weighed a mean of 33.6 kg (SD: 10.5) and the mean age at diagnosis was 36.7 months (31.3). A total of 17 breeds are considered; the most common breeds are the Rottweiler (4 dogs), the Labrador (9 dogs) and 10 mixed breed dogs. From Table 3.2, it is seen that of the 84 elbow joints pathologically, 60 (71.4%) were single frag-ment and 11 (13.1%) were fissures. The type of FPC is a coronoid tip in 52.4% and 61% of the elbow joints were dislocated. The mean area of the fragment was 0.159 (SD: 0.129). Table 3.3 shows that 54.8 % of the elbow joints have an IEWG score of 0. The mean TNS score is 0.5 (SD: 0.1). In older dogs (at least 72 months old), 11.1 % of 18 elbow joints are pathologically fis-suric. In the younger dogs (4 to 12 months), the proportion is 23.1 % (see Table 3.4).  Table 4.13). Furthermore, the area of the fragment is almost twice as large on average when the limbs are affected by lameness (0.202 2 to 0.112

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In Table 3.7 and 4.2 (as well as Figure 4.1) it can be seen that the TNS value is slightly lower if the elbow joint shows the lameness grade 0. On average, the TNS value is 0.460, while the mean value for the elbow joints with lameness grade is 0.481. The median, as well as the 1st and 3rd quartiles are also smaller in the group of elbow joints with lameness grade 0. According to Table 4.5, the area of the fragment is slightly larger if the dog is between 4 and 12 months. The median is 0.03 2 larger in the group (0.15 to 0.12 2 ) and the arithmetic mean is 0.02 2 larger. In Table 4.6 as well as Figure 4.3, it is observed that the area of the fragment is larger in the group of elbow joints affected by lameness. Minimum, 1st quartile, median, 3rd quartile, maximum and mean are larger in this group. The median in the group is 0.16, while the median in the group of elbow joints without lameness is 0.09. In the group of elbow joints without lameness degree, the 3rd quartile is only 0.15. In Table 4.13 it is visible that only one dog has a dislocated elbow joint with lameness grade 0 and a nondislocated elbow joint with a lameness grade between 1 and 5. However, the opposite is true in 18 dogs, so that dislocated elbow joints are present much more frequently if the elbow joints are also affected by lameness. Table 4.14 shows that an irregular shape occurs less frequently in the elbow joints without lameness group (7.1 %) than in the group with lameness (16.7 %). In the group of elbow joints without lameness, the pointed shape is dominant (35.7 %), while in the group of elbow joints with lameness it is the second least common shape with 21.4 %.